JP2022188505A - Printing device - Google Patents

Abstract

To provide a printing device that can suppress variation of ink pressure values in a nozzle at the time of executing a printing job, so as to improve printing quality.SOLUTION: A printing device comprises an injection part configured to include an ink chamber forming a portion of a circulation flow passage and a nozzle for injecting ink in the ink chamber, and a control part that controls circulation of ink flowing through the circulation flow passage. The control part performs control by which injection amounts of ink in a printing job are calculated before executing the printing job, inflow of ink into the ink chamber is determined on the basis of the calculated injection amounts of ink and the determined inflow is maintained during execution of the printing job.SELECTED DRAWING: Figure 10

Description

The present disclosure relates to an inkjet printing device with an ink circulation arrangement.

2. Description of the Related Art Among inkjet printers, there is known a circulating printer that circulates ink between an inkjet head and an ink tank. In such a circulating printing apparatus, a method of changing the amount of ink supplied to the inkjet head according to the amount of ink ejected from the nozzles of the inkjet head when executing a print job has been proposed (see, for example, Patent Document 1).

JP 2019-14194 A

FIG. 7A is a graph showing chronological changes in Qin, Qout, and Qjob when a print job is executed by a conventional method, and FIG. , and Pnozzle, and FIG. 7C is a graph showing time-series changes in print density when a print job is executed.

Here, Qin and Pin are the ink flow rate and ink pressure value at the ink supply port of the inkjet head, Qout and Pout are the ink flow rate and ink pressure value at the ink discharge port, and Qjob is the is the amount of ink ejected from a nozzle, and Pnozzle is the ink pressure value at the nozzle.

As shown in FIG. 7A, Qjob increases as ink is ejected from the nozzles as the print job is executed. In the conventional method, Pin is controlled as shown in FIG. 7B so that Qin increases as Qjob increases. At this time, as shown in FIG. 7B, Pnozzle decreases due to ink ejection from the nozzles. This is because when ink is ejected from a nozzle by applying a force greater than the atmospheric pressure in the direction of ejection, due to the law of action and reaction, the positive pressure in the ejection direction acts in the opposite direction inside the nozzle, creating a negative pressure. This is because it becomes larger.

The value of Pnozzle affects the droplet size of ink ejected from a nozzle (the amount of ink ejected in one ejection). Therefore, when the value of Pnozzle fluctuates, the size of ink droplets ejected from the nozzles fluctuates, resulting in fluctuations in print density (ink density in the image on the recording medium). For example, when the value of Pnozzle becomes small, the droplet size becomes small, the amount of ink that lands on the recording medium becomes small, and the print density becomes low. As a result, as shown in FIG. 7(c), the print density fluctuates, which leads to streaks, unevenness, etc., and lowers the print quality.

As described above, in the conventional method, when a print job is executed, there is a risk that the ink pressure value in the nozzles will fluctuate according to the ejection of ink from the nozzles, resulting in deterioration in print quality.

The present disclosure has been made in view of the above problem, and an object of the present disclosure is to provide a printing apparatus capable of suppressing fluctuations in ink pressure values at nozzles during execution of a print job and improving print quality.

A printing apparatus according to one aspect of the present disclosure includes an ink chamber forming a part of a circulation flow path, an ejection section configured to include nozzles for ejecting ink in the ink chamber, and a circulation of ink flowing through the circulation flow path. wherein the control unit calculates the ink ejection amount in the print job before execution of the print job, and the amount of ink flowing into the ink chamber based on the calculated ink ejection amount. is determined, and control is performed to maintain the determined inflow amount during execution of the print job.

Further, in the printing apparatus, when a plurality of print jobs are to be continuously executed, the control unit determines the amount of ink flowing into the ink chamber for each print job before executing the continuous printing, The amount of ink flowing into the ink chamber may be switched at the time of switching.

Further, in the printing apparatus, the control unit may circulate ink at a predetermined circulation flow rate during standby for printing.

The printing apparatus further includes a storage unit that stores correspondence information that associates ink temperatures with circulation flow rates, and a detection unit that detects the temperature of the ink flowing through the circulation flow path. A circulation flow rate of ink flowing through the circulation path may be determined based on the detected ink temperature and the correspondence information, and an inflow amount of ink into the ink chamber may be determined based on the ink ejection amount and the circulation flow rate. .

Further, the printing apparatus further includes a storage unit that stores correspondence information that associates the temperature of the injection unit with the circulation flow rate, and a detection unit that detects the temperature of the injection unit. A circulation flow rate of ink flowing through the circulation path is determined based on the detected temperature of the ejecting section and the corresponding information, and an inflow amount of ink into the ink chamber is determined based on the ink ejection amount and the circulation flow rate. good too.

Further, the printing apparatus further includes a storage unit that stores correspondence information that associates ink viscosity and circulation flow rate, and a detection unit that detects the viscosity of ink flowing through the circulation flow path, and the control unit , the circulation flow rate of the ink flowing through the circulation path is determined based on the detected ink viscosity and the correspondence information, and the ink flow rate into the ink chamber is determined based on the ink ejection amount and the circulation flow rate. good.

The printing apparatus further includes a display unit and an input unit, and the control unit causes the display unit to display the circulation flow rate of the ink flowing through the circulation path, and controls the circulation according to the user input received by the input unit. The circulation flow rate of ink flowing through the path may be changed.

Further, the printing apparatus includes a first ink reservoir having an air layer connected to the ink supply port of the ejection section, and a second ink reservoir having an air layer connected to the ink discharge port of the ejection section. and an air pressure control for controlling the pressure of the air layer of the first ink reservoir and the air layer of the second ink reservoir, wherein the air pressure control section produces a differential pressure between the two air layers. The circulating flow rate of the ink flowing through the circulation path may be controlled by controlling the flow rate of the ink.

Further, the printing apparatus may further include a liquid pump provided at the ink supply port of the ejection section, and the circulation flow rate of the ink flowing through the circulation path may be controlled by the liquid pump pressure of the liquid pump.

Further, in the printing apparatus, the control unit determines the amount of ink flowing into the ink chamber from the circulation flow rate of the ink flowing through the circulation channel and the average value of the ink ejection amount during execution of the print job. You can do it.

According to the printing apparatus of the present disclosure, fluctuations in the ink pressure value at the nozzles during execution of a print job are suppressed, so print quality can be improved.

1 is a diagram showing the main configuration of a printer 1; FIG. FIG. 2(a) is a schematic diagram of the internal configuration of the head unit 24 when the head unit 24 is viewed from the side. FIG. 2B is a schematic diagram of the head unit 24 when viewed from the recording medium side. FIG. 3 is a schematic diagram showing the main configuration of the ink circulation mechanism 300 of the printing apparatus 1 and the connections between the parts of the ink circulation mechanism 300. As shown in FIG. FIG. 4 is a schematic diagram showing the internal configuration of the inkjet head 51. As shown in FIG. FIG. 5 is a schematic diagram showing details of part A in FIG. FIG. 6A is a graph showing ink flow rates during printing standby. FIG. 6B is a graph showing ink pressure values during printing standby. FIG. 7A is a graph showing fluctuations in ink flow during execution of a print job in the prior art. FIG. 7B is a graph showing fluctuations in the ink pressure value during execution of a print job in the prior art. FIG. 7C is a graph showing variations in print density when a print job is executed in the conventional technology. FIG. 8A is a graph showing fluctuations in the ink flow rate during execution of a print job in the printing apparatus 1. FIG. FIG. 8B is a graph showing fluctuations in the ink pressure value during execution of a print job in the printing apparatus 1. FIG. FIG. 8C is a graph showing variations in print density when a print job is executed in the printing apparatus 1. FIG. FIG. 9 is a block diagram showing a control configuration for ink flow rate control. FIG. 10 is a flow chart of ink flow rate control. FIG. 11 is a block diagram showing a control configuration for ink flow rate control. FIG. 12A shows an example of the correspondence relationship between the ink temperature and the ink flow rate during standby. FIG. 12B shows an example of the correspondence relationship between the head temperature and the ink flow rate during standby. FIG. 12(c) shows an example of the correspondence relationship between the ink viscosity and the ink flow rate during standby. FIG. 13 is a block diagram showing a control configuration for ink flow rate control. FIG. 14 is a schematic diagram showing the main configuration of the ink circulation mechanism 400 of the printing apparatus 1 and connections between the parts of the ink circulation mechanism 400. As shown in FIG.

A printing apparatus according to the present disclosure will be described below with reference to the drawings. In addition, in the following description, the same reference numerals are given to the components having the same function and configuration, and the description thereof will be omitted.
[1] Embodiment (1) Printer 1
FIG. 1 is a diagram showing the overall configuration of a printing device 1 that is an embodiment of the present disclosure. As shown in FIG. 1 , the printing apparatus 1 includes a paper feeding section 10 , an image forming section 20 , a paper discharging section 30 and a control section 40 .

(1-1) Paper feed section 10
The paper feeding section 10 supplies the recording medium P on which image formation is to be performed to the image forming section. The paper feed unit 10 includes a paper feed tray 11 that holds the recording medium P and a transport unit 12 that supplies the recording medium P to the image forming unit 20 .

The paper feed tray 11 is a plate-like member on which one or more recording media P can be placed. The paper feed tray 11 is provided so as to move up and down according to the amount of the placed recording media P, and is held at a position where the uppermost recording medium P is transported by the transport unit 12 .

The conveying unit 12 feeds the uppermost recording medium P placed on the paper feed tray 11 onto the belt 123 and drives the belt 123 to rotate by rollers 121 and 122 to convey the recording medium P on the belt 123 . do.

(1-2) Image forming section 20
The image forming section 20 ejects ink onto the recording medium P supplied from the paper feeding section 10 to form an image. The image forming section 20 includes an image forming drum 21 , a delivery unit 22 , a sheet heating section 23 , a head unit 24 , an irradiation section 25 and a delivery section 26 .

The image forming drum 21 carries the recording medium P along its cylindrical outer peripheral surface, and conveys the recording medium P as it rotates counterclockwise in the figure. The outer peripheral surface of the image forming drum 21 faces the sheet heating section 23 , the head unit 24 and the irradiation section 25 .

The transfer unit 22 transfers the recording medium P conveyed by the conveying section 12 to the image forming drum 21 . The transfer unit 22 includes a swing arm portion 221 for carrying one end of the recording medium P, a cylindrical transfer drum 222 , and the like. P is guided along the outer peripheral surface of the image forming drum 21 and transferred to the image forming drum 21 .

The paper heating section 23 heats the recording medium P carried by the image forming drum 21 . The paper heating unit 23 has, for example, an infrared heater that generates heat when energized. The paper heating unit 23 is provided in the vicinity of the outer peripheral surface of the image forming drum 21 and upstream of the head unit 24 in the conveying direction of the recording medium P. As shown in FIG. The paper heating unit 23 controls its heat generation by the control unit 40 so that the recording medium P carried by the image forming drum 21 and passing near the paper heating unit 23 reaches a predetermined temperature.

The head unit 24 ejects ink onto the recording medium P carried by the image forming drum 21 to form an image. The head units 24 are individually provided for each of the colors Y (yellow), M (magenta), C (cyan), and K (black). In FIG. 1, the head units 24 corresponding to the respective colors of Y, M, C, and K are provided in order from upstream in the conveying direction of the recording medium P. As shown in FIG. A detailed configuration of the head unit 24 will be described later.

After the ink is ejected onto the recording medium P, the irradiation unit 25 irradiates the recording medium P with an energy beam for curing the ink. The irradiation unit 25 includes, for example, a fluorescent tube such as a low-pressure mercury lamp. The irradiation unit 25 is provided in the vicinity of the outer peripheral surface of the image forming drum 21 and downstream of the head unit 24 in the conveying direction of the recording medium P. As shown in FIG.

The irradiation unit 25 may be any device that emits energy rays that cure the ink according to the properties of the ink. A metal halide lamp, a light emitting diode, or the like can be used.

The delivery section 26 conveys the recording medium P from the image forming drum 21 to the paper discharge section 30 . The delivery unit 26 transfers the recording medium P carried by the image forming drum 21 to the belt 263 by the transfer drum 264 , and the belt 263 is rotationally driven by rollers 261 and 262 to convey the recording medium P on the belt 263 .

(1-3) Paper discharge unit 30
The paper discharge unit 30 includes a plate-shaped paper discharge tray 31 and stores the recording medium P conveyed from the image forming unit 20 .

(1-4) Control unit 40
The control unit 40 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Various programs stored in the ROM are read out and developed in the RAM, and the programs developed in the RAM are executed by the CPU. Control the action.

(2) Head unit 24
Details of the head unit 24 will be described.

(2-1) Head unit 24
FIG. 2(a) is a schematic diagram of the internal configuration of the head unit 24 when the head unit 24 is viewed from the side. FIG. 2B is a schematic diagram of the head unit 24 when viewed from the side of the recording medium P carried by the image forming drum 21 .

The head unit 24 is provided with a length (width) that covers the entire recording medium P in the direction perpendicular to the conveying direction of the recording medium P (width direction: arrow X direction).

The head unit 24 has a plurality of inkjet heads 51 . In the illustrated example, one head unit 24 is provided with 16 inkjet heads 51 . Each of the 16 ink jet heads 51 constitutes 8 ink head modules 52 in which two ink jet heads 51 are grouped together.

Each inkjet head 51 has a plurality of nozzles 511 . The inkjet head 51 forms an image on the recording medium P by ejecting ink from a plurality of nozzles 511 . Accordingly, the inkjet head 51 is provided with a plurality of nozzles 511 exposed to the lower surface side of the head unit 24 so as to face the recording medium P carried by the image forming drum 21 .

The head unit 24 includes an ink tank 53 that stores ink to be supplied to the inkjet head 51 .
The ink tank 53 includes a main tank 54 that stores ink supplied from an ink supply unit (ink cartridge), a first sub-tank 55 that supplies the ink supplied from the main tank to the inkjet head 51, and ink collected from the inkjet head 51. is configured to include a second sub-tank 56 that stores the .

In FIG. 2A, the main tank 54 is provided in the central portion of the ink tank 53 in the longitudinal direction, the first sub-tank 55 is provided on both edges thereof, and the second sub-tank 56 is provided on both edges thereof. However, the number and arrangement of the main tank 54, the first sub-tank 55, and the second sub-tank 56 may be appropriately changed according to the number of the inkjet modules 52 and the like.

(2-2) Ink circulation mechanism 300
FIG. 3 is a schematic diagram showing the main configuration of the ink circulation mechanism 300 in the printing apparatus 1 and the connection between each part of the ink ejection mechanism.

The ink circulation mechanism 300 includes an inkjet head 51, a main tank 54, a first sub-tank 55, a second sub-tank 56, a degassing module 61, a filter 62, air pressure controllers 65 and 66, and the like.

The main tank 54 and the first sub-tank 55 are connected by a path 301, the first sub-tank 55 and the inkjet head 51 are connected by a path 302, the inkjet head 51 and the second sub-tank 56 are connected by a path 303, and the second The sub-tank 56 and the main tank 54 are connected by a path 304 . Each of the paths 301 to 304 is a tubular member through which ink passes, and is made of resin or the like, for example.

The inkjet head 51 ejects part of the ink supplied from the first sub-tank 55 through the nozzles 511 and discharges the remaining ink to the second sub-tank 56 . Details of the inkjet head 51 will be described later.

The main tank 54 stores ink to be circulated to each part of the ink circulation mechanism 300 .

The first sub-tank 55 stores ink supplied from the main tank 54 , and the stored ink is supplied to the inkjet head 51 . The first sub-tank 55 is a tank-like container that is sealed except for various connection points, and is formed with an ink layer 55a and an air layer 55b.

The second sub-tank 56 stores ink collected from the inkjet head 51 . The second sub-tank 56 is a tank-like container that is sealed except for various connection points, and is formed with an ink layer 56a and an air layer 56b.

A degassing module 61 is provided in the path 301 to degas the ink passing through the path 301 . The degassing module 61, for example, causes the ink to flow down to one side through the gas-permeable membrane, and reduces the pressure on the other side with a vacuum pump or the like, so that only the dissolved gas in the ink in contact with the gas-permeable membrane is permeable. It is configured to be removed through the membrane.

A filter 62 is provided in the path 302 to remove foreign matter such as dust contained in the ink passing through the path 302 . The pore diameter of the filter 62 is preferably a pore diameter that can remove foreign matter having a particle diameter equal to or larger than the nozzle diameter of the inkjet head 51 .

A pump 63 is provided in the path 301 . The pump 63 operates under the control of the control section 40 and supplies ink from the main tank 54 to the first sub-tank 55 . As the pump 63, for example, a positive displacement pump such as a diaphragm pump, a tube pump, or the like is used.

A pump 64 is provided in the path 304 . The pump 64 operates under the control of the control section 40 and supplies ink from the second sub-tank 56 to the main tank 54 . As the pump 64, for example, a positive displacement pump such as a diaphragm pump, a tube pump, or the like is used.

The air pressure control section 65 is connected to the first sub-tank 55 and adjusts the pressure of the air layer 55b in the first sub-tank 55 under the control of the control section 40 . The air pressure control section 66 is connected to the second sub-tank 56 and adjusts the pressure of the air layer 56b in the second sub-tank 56 under the control of the control section 40 . The flow rate of ink flowing from the first sub-tank 55 to the inkjet head 51 and from the inkjet head 51 to the second sub-tank 56 is adjusted by the control of the air pressure controller 65 and the air pressure controller 66 . In addition, the air pressure control unit 65 and the air pressure control unit 66 control the nozzles 511 of the inkjet head 51, the ink supply port 512 (see FIG. 4), and the ink discharge port 514 (see FIG. 4) to a negative pressure state. This prevents ink from leaking from the nozzles when image formation or various maintenance is not performed.

With the above configuration, the ink circulates among the main tank 54 - first sub-tank 55 - inkjet head 51 - second sub-tank 56 .
(2-3) Inkjet head 51
FIG. 4 is a schematic diagram showing the internal configuration of the inkjet head 51. As shown in FIG.

As shown in the figure, the inkjet head 51 includes nozzles 511 , supply ports 512 , ink chambers 513 and discharge ports 514 .

Ink supplied from the first sub-tank 55 sequentially passes through a supply port 512, an ink chamber 513, and a discharge port 514 that form part of the ink circulation path (see arrow B), and is collected in the second sub-tank 56. . A part of the ink flowing into the ink chamber 513 is ejected from the nozzle 511 onto the recording medium when the print job is executed. FIG. 5 shows details of part A in FIG. Nozzle 511 has an ink channel 515 that communicates with ink chamber 513 . The nozzle inner wall 516 is formed using a piezoelectric (piezo) element, and is shear-deformed according to a pulse signal supplied under the control of the control unit 40 to eject the ink in the ink channel 515 from the nozzle port 517 .

(2-4) Ink Flow Control Here, the ink flow rate and ink pressure value at the ink supply port 512 of the inkjet head 51 are assumed to be Q _in and P _in . Further, the ink flow rate and ink pressure value at the ink discharge port 514 are Q _out and P _out , the ink discharge amount from the nozzle 511 during print job execution is Q _job , and the ink pressure value at the nozzle port 511 is P _nozzle .

FIG. 6(a) is a graph showing time-series changes in Q _in and Q _out during print standby, and FIG. 6(b) is a time-series change in P _in , P _out and P _nozzle during print job execution. is a graph showing

As shown in FIG. 6A, Q _in and Q _out are constant values during printing standby, and a constant amount of ink circulates in the ink circulation mechanism 300 . At this time, P _in , P _out and P _nozzle are in a negative pressure state as shown in FIG. By adjusting the pressure of the air layer 55b in the first sub-tank 55 and the pressure of the air layer 56b in the second sub-tank 56 so that P _in >P _out , An ink flow is created and Q _in and Q _out are adjusted according to the differential pressure.

FIG. 7A is a graph showing chronological changes in Q _in , Q _out , and Q _job when a print job is executed by a conventional method as a comparative example, and FIG. 7A and 7B are graphs showing time-series changes in P _in , P _out , and P _nozzle during execution, and FIG. 7C is a graph showing time-series changes in print density during print job execution.

As shown in FIG. 7A, Q _job increases as ink is ejected from the nozzles 511 as the print job is executed. In the comparative example, P _in is controlled as shown in FIG. 7B so that Q _in increases as Q _job increases. At this time, as shown in FIG. 7(b), the injection of ink from the nozzle port 511 causes P _nozzle to drop. The droplet size of the ink ejected from the nozzle fluctuates in accordance with the fluctuation of the P _nozzle , which causes fluctuations in print density as shown in FIG.

FIG. 8A is a graph showing chronological changes in Q _in , Q _out , and Q _job when the printing apparatus 1 of the present disclosure executes a print job, and FIG. FIG. 8C is a graph showing time-series changes in P _in , P _out , and P _nozzle in , and FIG. 8C is a graph showing time-series changes in print density when a print job is executed. In addition, in FIG.8(b) and FIG.8(c), a broken line shows a comparative example.

As shown in FIG. 8A, in the printing apparatus 1 of the present disclosure, as in the comparative example, when a print job is executed, Q _job is increased by ejecting ink from the nozzles 511 in accordance with the execution of the print job. do. On the other hand, during the execution of the job, Qin is controlled to maintain a constant value _{larger than Qout during} the ink flow rate maintenance period including the predetermined time before and after the ink is actually ejected from the nozzles 511. be. For example, let Q _standby be the ink flow rate during standby, and <Q> _job be the average amount of ink ejected in a print job (the total amount of ink ejected divided by the ink flow rate maintenance period), then Q _out =Q _standby , and Q _in = Q _standby + <Q> _job . In the printing apparatus 1 of the present disclosure, P _in is controlled such that Q _in is constant during the ink flow rate maintenance period. Since Q _in depends on the values of P _in , P _out and P _nozzle , P _in is controlled so that Q _in remains constant even with fluctuations in P _nozzle . At this time, as shown in the _solid line _{graph in} FIG. The amount of decrease is smaller than in the comparative example of the dashed line graph. When the P _nozzle fluctuation becomes smaller, the print density fluctuation also becomes smaller as shown in FIG.

FIG. 9 is a control block diagram of ink flow rate control. Upon receiving the print job data, the control unit 40 analyzes the print job data before execution of the print job, obtains the total amount of ink to be ejected when the print job is executed, and uses the obtained total amount of ink to calculate the amount of ink during the ink amount maintenance period. Calculate the ink ejection amount average <Q> _job . Then, the ink flow rate during printing is set so that the ink flow rate during standby Q _standby + the average ink ejection amount <Q> _job . In addition, the control unit 40 analyzes the print job data, obtains the timing at which the ink is calculated and the amount of ink ejected at each timing, and maintains the ink flow rate during printing set at each timing constant. Determine the required P _in . After that, the execution of the print job is started, and during the execution of the print job, by controlling the air pressure control unit 65 at each timing so that P _in is determined in advance, during the ink flow rate maintenance period, the set The ink flow rate during printing is maintained.

Note that the ink amount maintenance period is determined by analyzing the print job data, determining the timing at which the ink is calculated, and determining the timing from a predetermined time before the timing at which the first ink is ejected to a predetermined time after the timing at which the last ink is ejected. is required as a period of

When continuously executing a plurality of print jobs, the control unit 40 receives the job data of the plurality of print jobs before the continuous execution, and determines the ink flow rate during printing for each print job based on the received job data. to decide. After that, when the print job is switched, control is performed to switch the ink flow rate during printing to the one determined before the continuous execution.

Here, the print job refers to printing (image formation) of a print image for one page on a recording medium. Therefore, when printing a plurality of pages, a plurality of print jobs are continuously executed.

FIG. 10 is a flowchart of ink flow rate control executed by the control unit 40 when a print job of the printing apparatus 1 is executed.

Until the print job data is received (step S1: No), the control unit 40 is _in a printing standby state, and sets the ink flow rate Qin to the standby ink flow rate Q _standby (step S6). The controller 40 controls the air pressure controllers 65 and 66 so that the ink flow rate Qin maintains the _standby ink flow rate _Qstandby during the print standby state.

When the control unit 40 receives the print job data (step S1: Yes), it analyzes the print job data and determines the ink flow rate during job execution (Q _standby +<Q> _job ) (step S2). When continuously executing a plurality of print jobs, the control unit 40 determines the ink flow rate during execution of each print job.

The control unit 40 sets the ink flow rate Qin to the job execution ink flow rate (Q _standby +<Q> _job ) according to the print job to be executed next (step S3).

The control unit 40 starts execution of the print job, and while the print job is being executed (ink flow rate maintenance period), the ink flow rate Q _in reaches the job execution ink flow rate (Q _standby + <Q> _job ) is controlled (step S4).

After executing the print job, the control unit 40 determines whether or not execution of all jobs has ended. If not (step S5: No), go to step S3.

The control unit 40 controls the ink flow rate in the inkjet head 51 according to the procedure described above. This ink flow rate control suppresses fluctuations in the ink pressure value at the nozzles 511 during execution of a print job, thereby improving print quality.
[2] Modifications The present disclosure has been described above based on the embodiments, but the present disclosure is of course not limited to the above-described embodiments, and the following modifications can be implemented. .

(1) The ink flow rate Q _standby during printing standby in the above-described embodiment is a predetermined constant value, but the standby ink flow rate Q _standby may be appropriately changed according to the situation. For example, the standby ink flow rate Q _standby may be changed according to the ink temperature, head temperature, or ink viscosity.

FIG. 11 is a control block diagram of ink flow rate control for changing the standby ink flow rate according to the ink temperature, head temperature, and ink viscosity. The control unit 40 includes a CPU 41 and a nonvolatile memory 41. The nonvolatile memory 42 stores correspondence information 43 between the ink temperature, the head temperature, the ink viscosity, and the standby ink flow rate Qstandby. Further, the inkjet head 51 is provided with a head temperature sensor 72 that detects the temperature of the inkjet head 51 . Alternatively, an ink temperature sensor 71 that detects the temperature of the circulating ink or an ink viscosity sensor 73 that detects the viscosity of the circulating ink is provided at an arbitrary location in the ink circulation mechanism 300 .

The ink temperature sensor 71 , the head temperature sensor 72 , and the ink viscosity sensor 73 are connected to the control unit and transmit the detected ink temperature, head temperature, and ink viscosity to the control unit 40 . The control unit 40 determines the standby ink amount Q _standby based on the correspondence information 43 .

The controller 40 may determine the standby ink flow rate based on correspondence information 43, an example of which is shown in FIG. 12(a). FIG. 12A shows an example of correspondence 43 indicating the correspondence between the ink temperature T _ink received from the ink temperature sensor 71 and the standby ink flow rate Q _standby . In the figure, T1, T2, T3, and T4 are constants representing predetermined temperatures that satisfy T1<T2<T3<T4. Q0, Q1, and Q2 are constants representing predetermined ink flow rates, respectively, and Q1 and Q2 satisfy Q2>Q1.

When T _ink ≤ T1, the control unit 40 sets the standby ink flow rate Q _standby to Q0+Q2. When T1<T _ink ≦T2, the controller 40 sets the standby ink flow rate Q _standby to Q0+Q1. When T2<T _ink ≦T3, the controller 40 sets the standby ink flow rate Q _standby to Q0. When T3<T _ink ≦T4, the control unit 40 sets the standby ink flow rate Q _standby to Q0−Q1. When T4<T _ink , the controller 40 sets the standby ink flow rate Q _standby to Q0-Q2.

Since the fluidity of the ink changes depending on the ink temperature, by controlling the circulation flow rate according to the ink temperature, the ink can be circulated smoothly, the ink ejection operation can be stabilized, and the printing quality can be improved.

The controller 40 may determine the standby ink flow rate based on correspondence information 43, an example of which is shown in FIG. 12(b). FIG. 12(b) shows an example of a correspondence relationship 43 indicating the correspondence relationship between the ink temperature T _head received from the head temperature sensor 72 and the standby ink flow rate Q _standby . In the figure, T1, T2, T3, and T4 are constants indicating predetermined temperatures that satisfy T1<T2<T3<T4. Q0, Q1, and Q2 are constants indicating predetermined ink flow rates, respectively, and Q1 and Q2 satisfy Q2>Q1.

When T _head ≤ T1, the controller 40 sets the standby ink flow rate Q _standby to Q0+Q2. When T1<T _head ≦T2, the controller 40 sets the standby ink flow rate Q _standby to Q0+Q1. When T2<T _head ≦T3, the controller 40 sets the standby ink flow rate Q _standby to Q0. When T3<T _head ≦T4, the controller 40 sets the standby ink flow rate Q _standby to Q0−Q1. When T4<T _head , the controller 40 sets the standby ink flow rate Q _standby to Q0-Q2.

The temperature of the ink flowing through the circulation path changes depending on the head temperature, and the fluidity of the ink changes depending on the ink temperature. Therefore, by controlling the circulation flow rate according to the ink temperature, the ink circulation is performed smoothly, and the ink is ejected. You can stabilize the operation and improve the print quality.

The controller 40 may determine the standby ink flow rate based on correspondence information 43, an example of which is shown in FIG. 12(c). FIG. 12(c) shows an example of the correspondence 43 indicating the correspondence between the ink viscosity η received from the ink viscosity sensor 73 and the standby ink flow rate Q _standby . In the figure, η1, η2, η3, and η4 are constants representing predetermined viscosities that satisfy η1<η2<η3<η4. Q0, Q1, and Q2 are constants representing predetermined ink flow rates, respectively, and Q1 and Q2 satisfy Q2>Q1.

When η≦η1, the controller 40 sets the standby ink flow rate Q _standby to Q0+Q2. When η1<η≦η2, the controller 40 sets the standby ink flow rate Q _standby to Q0+Q1. When η2<η≦η3, the controller 40 sets the standby ink flow rate Q _standby to Q0. When η3<η≦η4, the controller 40 sets the standby ink flow rate Q _standby to Q0−Q1. When η4<η, the controller 40 sets the standby ink flow rate Q _standby to Q0-Q2.

By controlling the circulation flow rate according to the ink viscosity, it is possible to smoothly circulate the ink, stabilize the ink ejection operation, and improve the print quality.

(2) The ink flow rate Q _standby during printing standby in the above-described embodiment is a predetermined constant value, but the standby ink flow rate Q _standby is determined according to the user's input indicating the ink flow rate during standby. You may FIG. 13 is a control block diagram of ink flow rate control for changing the standby ink flow rate according to user input. The control unit 40 receives a user input instructing the standby ink flow rate from the operation panel 81, and sets the standby ink flow rate Q _standby based on the received user input.

The user input may be received in the form of specifying the absolute amount of ink flow during standby. For example, the operation panel 81 displays a selection to select from a plurality of items such as "high", "high", "standard", "low", "low", etc. for the standby ink flow rate, and the standby ink flow rate corresponding to the selected item is displayed. A flow rate Q _standby may be set. When "high" is selected, the standby ink flow rate Q _standby is set to Q0+Q2. Similarly, when "large", "standard", "small", and "small" are selected, the standby ink flow rate Q _standby is set to Q0+Q1, Q0, Q0-Q1, and Q0-Q2, respectively. Here, Q0, Q1, and Q2 are constants representing predetermined ink flow rates, respectively, and Q1 and Q2 satisfy Q2>Q1.

User input may be received in the form of specifying a relative change from the current standby ink flow rate. For example, the current standby ink flow rate is displayed on the operation panel 81, and a user input designating whether to "increase" or "decrease" the standby ink flow rate is received. may be set. That is, when the current standby ink flow rate Q _standby is Q0 and the user input to "increase" the standby ink flow rate is received, the standby ink flow rate Q _standby is set to Q0+Q1 and the user input to "decrease" is received. is received, the standby ink flow rate Q _standby may be set to Q0-Q1. Here, Q1 is a constant representing a predetermined ink flow rate.

(3) In the ink circulation mechanism 300 described above, the ink collected in the second sub-tank 56 from the inkjet head 51 is supplied to the main tank 54, but the configuration is not limited to this. Like the ink circulation mechanism 400 shown in FIG. 14, a path 401 connecting the first sub-tank 55 and the second sub-tank 56 is provided, and the ink recovered from the inkjet head 51 to the second sub-tank 56 is supplied to the first sub-tank 55. You can do it.

(4) In the above-described embodiment, the air pressure controllers 65 and 66 control the air pressure of the air layer 55b of the first sub-tank 55 and the air layer 56 of the second sub-tank 56 to control the difference between the air layers 55b and 56b. Although the ink supply port 512 of the inkjet head 51 is provided with a liquid pump, the amount of ink flowing into the ink chamber 513 may be adjusted by the liquid supply pressure of the liquid pump. good. Alternatively, the ink discharge port 512 of the inkjet head 51 may be provided with a liquid pump, and the amount of ink discharged from the ink chamber 513 may be adjusted by the liquid pump pressure of the liquid pump.

(5) In the above embodiment, the printing apparatus 1 is configured by arranging a plurality of inkjet heads 51 in the head unit 24 provided with a width that covers the entire recording medium P in the width direction of the recording medium P. Although the single-pass type (line head type) ink jet printing apparatus has been described, it may be a multi-pass type (serial head type) ink jet printing apparatus.

INDUSTRIAL APPLICABILITY The present disclosure is applicable to inkjet printing devices.

REFERENCE SIGNS LIST 10 paper feeding unit 20 image forming unit 30 paper discharging unit 40 control unit 24 head unit 51 inkjet head 53 ink tank

Claims (10)

an ejection section including an ink chamber that forms a part of the circulation flow path and a nozzle that ejects the ink in the ink chamber;
a control unit that controls the circulation of the ink flowing through the circulation channel;
The control unit calculates an ink ejection amount in the print job before execution of the print job, determines an amount of ink flowing into the ink chamber based on the calculated ink ejection amount, and determines an amount of ink flowing into the ink chamber based on the calculated ink ejection amount. A printing apparatus characterized by performing control to maintain the determined amount of inflow. When continuously executing a plurality of print jobs, the control unit determines the amount of ink to flow into the ink chamber for each print job before executing the continuous print, and determines the amount of ink to flow into the ink chamber when the print job to be executed is switched. 2. The printing apparatus according to claim 1, wherein the amount of inflow of ink from is switched. 2. The printing apparatus according to claim 1, wherein the control unit circulates the ink at a predetermined circulation flow rate while waiting for printing. a storage unit that stores correspondence information that associates the ink temperature with the circulation flow rate;
a detection unit that detects the temperature of the ink flowing through the circulation flow path,
The control unit determines a circulation flow rate of ink flowing through the circulation path based on the detected ink temperature and the corresponding information, and determines an inflow rate of ink into the ink chamber based on the ink ejection amount and the circulation flow rate. 3. The printing apparatus according to claim 1, further comprising: determining. a storage unit that stores correspondence information that associates the temperature of the injection unit with the circulation flow rate;
a detection unit that detects the temperature of the injection unit,
The control unit determines a circulation flow rate of ink flowing through the circulation path based on the detected temperature of the ejector and the corresponding information, and allows ink to flow into the ink chamber based on the ink ejection amount and the circulation flow rate. 3. A printing device according to claim 1 or 2, characterized in that it determines an amount. a storage unit that stores correspondence information that associates the ink viscosity with the circulation flow rate;
a detection unit that detects the viscosity of the ink flowing through the circulation flow path,
The controller determines a circulation flow rate of ink flowing through the circulation path based on the detected ink viscosity and the correspondence information, and determines an ink flow rate into the ink chamber based on the ink ejection amount and the circulation flow rate. 3. The printing apparatus according to claim 1, further comprising: determining. further comprising a display unit and an input unit;
The control unit causes the display unit to display a circulation flow rate of ink flowing through the circulation path, and changes the circulation flow rate of ink flowing through the circulation path according to a user input received by the input unit. 3. The printing apparatus according to 1 or 2. a first ink reservoir connected to the ink supply port of the ejection section and having an air layer;
a second ink reservoir connected to the ink outlet of the ejection section and having an air layer;
air pressure control for controlling the pressure of the air layer of the first ink reservoir and the air layer of the second ink reservoir;
3. The printing apparatus according to claim 1, wherein the pneumatic pressure control unit controls the circulation flow rate of the ink flowing through the circulation path by creating a differential pressure between two air layers. further comprising a liquid pump provided at the ink supply port of the ejection section;
3. The printing apparatus according to claim 1, wherein the circulation flow rate of ink flowing through the circulation path is controlled by the liquid feeding pressure of the liquid pump. The controller determines the amount of ink flowing into the ink chamber from the circulation flow rate of the ink flowing through the circulation channel and the average value of the ink ejection amount during execution of the print job. 3. The printing apparatus according to Item 1 or 2.

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